// 定义变量使用$
$high-light: yellow;
$basic-border: 1px solid black;

#app {
  // 还可以在css规则块内定义使用变量
  $width: 100px;

  background-color: $high-light;
  border: $basic-border;
  width: $width;
}

// 嵌套语法
a {
  color: black;
  &:hover {
    color: $high-light;
  }
}
